Continuous process for bleaching pigmented keratinous fibers



0 i967 A. E. DAVIS ETAL CONTINUOUS PROCESS FOR BLEACHING PIGMENTED KERATINOUS FIBERS Filed Aug. 25, 1964 i i 20 IO 9 0 min. 26 i & 7 W sque ezi nq 28 squefezing lain/sing Mordcnt B t Riising 44 S'ripping 'v q T lo 40 min.

Wetting IN VENTORS AGNES ELEANOR DAVIS ARNOLD M. SOOKNE BY mgzz Jaw/z ATTORNEYS United States Patent 3,350,160 CONTINUOUS PROCESS FOR BLEACHING PIGMENTED KERATINOUS FIBERS Agnes Eleanor Davis, Vienna, Va., and Arnold M.

Sookne, Silver Spring Md., assignors to Gillette Research Institute, Inc-., Washington, D.C., a corporation of Delaware Filed Aug. 25, 1964, Ser. No. 391,946 3 Claims. (Cl. 8-102) ABSTRACT OF THE DISCLOSURE Pigmented keratinous fibrous materials are bleached by passing a web-like belt of the fibrous material successively through an aqueous mordant solution containing a ferrous salt, an aqueous bleaching solution containing hydrogen peroxide and an aqueous solution of an iron removal reagent.

This invention relates to a novel continuous process for bleaching pigmented keratinous fibrous materials without impairing their desirable properties and to such a continuous process that is particularly adapted for commercial use.

The process involves the continuous bleaching of pigmented keratinous fibrous material, such as wool, karakul, alpaca, cashmere, vicuna, cow and goat hair and the like, or mixtures thereof to bleach the animal fibers to a light color by controlled application of a mordant, a bleach and a stripping bath under controlled conditions of temperature, concentration and time.-

All prior methods for bleaching pigmented keratinous materials, especially dark pigmented wool and hair fibers, were batch processes requiring long periods during which constant surveillance of the operation was necessary and personal judgment regarding adjustments of the system were required to be made. An example of such a batch process is the process described in United States Patent 2,914,374, Harris et al., assigned to applicants assignee.

Principal objects of the present invention are to provide a novel continuous method for bleaching of pigmented keratinous materials which eliminates the need for personnel surveillance and judgment and to provide for economical and complete use of chemicals in an automated commercially feasible system.

It is a further object of the present invention to provide a system and process which is interchangeably applicable to the bleaching of animal fibers in the loose condition or subsequent to fabrication 'of the fibers into textile webs.

.A further object of the present invention is to provide a process for the continuous bleaching of pigmented "keratinous fibrous materials without imparing the textile properties or the desirable handle of the treated animal fibers.

A further object is to provide such a process wherein pigmented keratinous material may be bleached white without serious deleterious effect on the quality of the material being treated.

These and other objects and advantages of the invention are provided by a continuous process for bleaching pigmented keratinous animal fibers which comprises forming the fibrous material to be bleached into a web-like belt, passing the fibrous belt through an aqueous mordant solution containing a ferrous salt maintained at a constant concentrationand temperature, passing the mordant solution treated fibrous belt through an aqueous bleaching solution maintained at a constant temperature and concentration and thereafter passing said fibrous belt through an aqueous solution of an iron-removal reagent main- -a relatively tained at a constant temperature and concentration and rinsing and drying the fibrous belt.

Throughout the specification and claims, keratinous fibrous material and fibrous belt are intended to mean keratinuous fibers such as cashmere, vicuna, alpaca, cow hair, goat hair, and the like in the raw stock state confined into a web either by fabricating the fibers into a textile by weaving or felting processes or by confining them between, for example, porous conveyor belts to prevent excessive motion of the fibers with respect to each other.

The invention will be more particularly described with reference to the accompanying drawing diagrammatically illustrating the process of the present invention and apparatus for carrying out said process.

In accordance with the invention, keratinous fibrous material either in the form of a woven or felted textile fabric illustrated by roll 10 or loose fibers maintained in the feed hopper 12 are fed between a pair of porous conveyor belts 14 and 16. The confined fibrous material is thoroughly wetted in passing below Wetting means 18 connected to a suitable source of wetting liquid which may contain a wetting agent in addition to water. Following the spray wetting, the fibrous material is squeezed by, for example, roll 20 and cooperating platen 22 and the fibrous material is passed through a tank 24 containing an aqueous mordant solution of a ferrous salt containing sulfuric acid maintained at a temperature of from about 100 to 200 F. The concentration of the aqueous mordant solution is maintained substantially constant by continuously circulating the solution from a storage source as indicated by the directional arrows. Further, conventional heating means may be maintained in the tank 24 or at the outlet from the source 'of mordant solution.

In the mordant step, the pH range of the solution should be between about '1 and about 3. It has been found that a pH greater than 3 may result in aerial oxidation of the ferrous ion at the relatively high temperature of the bath. As indicated above, the temperature of the solution in the mordant step may be in the range of 100 to 200 F. and a particularly useful range is from about '150 to about 170 F. By maintaining the mordant bath at such high temperature, the mordant treatment can be accomplished in a relatively short time, that is, from about 10 to about minutes although a time period up to 150 minutes may be used.

The liquor-to-stock ratio of the mordant bath may be varied substantially. For example, a liquor to stock ratio of 5 to 1 to to 1 or more will provide useful results. The concentration of the ferrous sulfate may also be varied substantially and useful results may be obtained in the range of from about 1 to about 20% as ferrous sulfate heptahydrate (FeSO -7H O) based on the weight of the bath. Further, other ferrous salts may be used in equivalent amounts; for example, ferrous acetate and ferrous ammonium sulfate have provided satisfactory results.

As the animal fibers leave the bath tank 24, the excess mordant solution is squeezed therefrom by squeeze roll 26 cooperating with platen 28. Thence, the fibers carried by the endless belts 14 and 16 are passed under spray head 30 and the fibers are thoroughly rinsed and cooled. The temperature of the fibers following the rinsing step should not be greater than, for example, 40 to about 80' F. to minimize oxidation of the ferrous ion.

Following the rinsing step, the belts 14 and 16- carry the fibers into tank 32 containing the bleaching solution. The bleaching step comprises the treatment of the fibers with a solution of hydrogen peroxide containing suitable buffering materials. It is important that the pH of the bleach bath be maintained within the range of about 7 to about 9 and preferably in the range of 7.5 to 8.5.

Preferred buffering materials for the bleach bath are tetra-sodium pyrophosphate and sodium tetraborate used in combination. The amount of hydrogen peroxide in the bleach solution may be varied from about .5 to about 5% calculated as 100% H based on the weight of the bath.

Other buffering materials may include sodium carbonate, sodium bicarbonae, sodium oxalate, etc.

The amount of tetrasodium pyrophosphate may be varied from about .5 to about 5% also based on the weight of the bath while the sodium tetraborate may vary from 0 to 5% based on the weight of the bath and a preferred mixture of buffers is 1 part tetrasodium pyrophosphate to 2.5 parts of sodium tetraborate.

The temperature of the bleaching bath is critical. For best retention of desirable fiber properties, the temperature of the bath should not be permitted to exceed 125 F. while a good working range is from about 100 to about 125 F.

The time required to achieve the desired color reduction in the animal fibers in the bleach tank 32 may range from about to about 90 minutes. The time requirement is determined to a large extent by (1) the initial coloration of the fibers, (2) the concentration of the hydrogen peroxide, and (3) the operating temperature of the bleaching bath. After the fibers have been bleached the required amount in the bleach tank 32, the endless belts 14 and 16 carrying the fibrous material are passed below the squeeze roll 34 which cooperates with the fixed platen 36 to remove excess bleach from the belt. Thereafter the belt is passed below the spray head 38 and the fibers are thoroughly rinsed in a water solution maintained at a temperature of from about 100 to about 150 F. to remove solubilized pigment, soluble iron and residual alkali and hydrogen peroxide.

After the rinsing step, the fibers are carried through tank 40 containing the strip bath, comprising an aqueous solution of an iron removal agent. The strip bath may be maintained at a temperature in the range of from about 125 to about 150 F., at a pH in the range of about 3.5 to about 4.5. Where the iron removal bath contains sodium formaldehyde sulfoxylate, a concentration of from about .2 to about 4.0 on the weight of the bath has been found to provide very satisfactory results. The time employed for thorough removal of any residual iron in the fibers may be in the range of from about 10 to about 40 minutes.

Other iron removal agents may be employed in the continuous process of the invention including, for example, oxalic acid.

Following the stripping step, the fibers are thoroughly rinsed while passing beneath spray heads 42. The final rinsing must be thorough to remove residual chemicals which may affect future processing of the fibers if the chemicals are allowed to remain on the fibers. Following the thorough rinsing, the bleached animal fibers are dried While passing through dryer means 44.

From the following description of an example of the continuous animal fiber bleaching process of the invention, it will be seen that the conditions generally required for a continuous process for bleaching pigmented keratinous animal fibers while retaining good mechanical properties are:

(1) A complete mordanting which may be accomplished with a relatively high concentration of ferrous sulfate heptahydrate maintained at a low pH.

(2) A relatively alkaline peroxide bleach in which the peroxide concentration is maintained substantially constant.

(3) A stripping step to insure complete removal of residual iron from the fibers.

Example 1 The following solutions were prepared:

Bath A0.05% Triton X 100 in water at 150 F., Bath B2.27% sulfuric acid and 3.1% ferrous sulfate heptahydrate in water at 150 F., pH 1.7,

Bath Cl% tetrasodium pyrophosphate, 2.5% sodium tetraborate and 1.25% hydrogen peroxide in water at 115 F., pH 8.3,

Bath D- 0.3% sodium formaldehyde sulfoxylate in water adjusted to pH 3.5 with sulfuric acid at 140 F.

Specimens of Black/ Brown Awassi carpet wool were arranged on a polypropylene netting A inch square openings) in thin layers, covered with an identical netting to hold the fibers in a fixed position and conveyed through the baths in the following manner:

At any instant the amount of fiber in any bath was such to produce a 24:1 bathzfiber ratio. The fiber-netting assembly was passed through Bath A to wet the fiber, squeezed through rollers at 60 lbs. pressure, then passed slowly through Bath B with an up-and-down motion for a period of 60 minutes during which time the pH was maintained at 1.7, the ferrous sulfate heptahydrate concentration was maintained at 3% and the temperature was maintained at 150 F. After 60 minutes of immersion in Bath B, the assembly passed through squeeze rollers at 60 lbs. pressure. The expressed liquor was returned to Bath B while the assembly proceeded through a forced spray of water at F. for 2 minutes, followed by squeezing through rollers at 60 lbs. pressure, and thence into Bath C which it moved through for 30 minutes. During the 30 minutes the hydrogen peroxide concentration was maintained at 1.25% and the pH maintained between 8.0 and 8.5 with additions of tetrasodium pyrophosphate and borax in the ratio of 112.5. The temperature was controlled at F.

From Bath C the assembly passed through squeeze rolls at 60 lbs. pressure, the expressed liquor being returned to Bath C, through a force spray of water at 150 F., through squeeze rolls at 60 lbs. pressure into Bath D through which it passed in 20 minutes with the temperature maintained at F., pH at 3.5 and sodium formaldehyde sulfoxylate concentration at 0.3%. After 20 minutes the assembly was squeezed at 60* lbs. pressure, force sprayed with water at F., squeezed at 60 lbs. pressure and air dried.

The treated fiber was cream color and uniformly bleached at the end of the processing train. The finished fibers had an ultimate elongation of 30% as compared with 29% for the untreated and a breaking strength of 1.25 grams per denier as compared with 1.27 grams per denier for the untreated fibers.

Example 2 The procedure of Example 1 was repeated except that Black/Brown Aleppo carpet wool was used. The wool was bleached to a creamy white and retained its desirable mechanical properties.

Example 3 The procedure of Example 1 was repeated except that Medium Grey Kandahar carpet wool was used. The wool was bleached to a clear white and retained good mechanical properties.

Example 4 The procedure of Example 1 was repeated with Black/ Brown Awassi carpet wool, except the wool was passed through Bath B in 30 minutes with the bath held at F. A bleached product was obtained similar to that produced by the procedure of Example 1.

Example 5 chanical properties.

Example 6 Without the aid of the polypropylene netting support a white wool fabric containing a small percentage of highly pigmented fibers was treated as in Example 5 except that Bath B contained 1.0% sulfuric acid and 2.0% ferrous sulfate heptahydrate at pH 2.0. The pigmented fibers were lightened in color to blend with the white wool fibers of the fabric and the hand and tensile propcrties of the bleached fabric remained unchanged.

Example 7 A specimen of the Black/Brown Awassi carpet WOOl of Example 1 was treated following the procedure of Example 1 exceptthe ferrous sulfate of Bath B was replaced with an equivalent amount of ferrous acetate and the sodium formaldehyde sulfoxylate of Bath D was replaced with an equivalent amount of oxalic acid.

The bleached color and the breaking strength of the treated fibers Were found to be equivalent to the color and breaking strength of the fibers treated in accordance with Example 1.

From the foregoing description of this invention, it will be seen that the continuous process for bleaching pigmented keratinous fibrous materials hereinabove described may be used with many types of keratinous materials. It will also be recognized that various modifications may be made in form of the apparatus employed in carrying out the process of the invention; for example, the wetting and rinsing steps of the process may be carried out in tanks similar to tanks 24 and 32 and the squeezing or extracting steps may be carried out between pairs of cooperating rolls or by passing the belt or web over a conventional suction box or the like.

It will also be visualized by those skilled in the art that the economic value of dark pigmented keratinous material such as dark alpaca or karakul is much less than that of material of lighter shades since the lighter shades can find substantially wider use and may be dyed to a greater variety of commercially desirable shades. Further, the amount of such dark materials produced in p the world is very large and the darker shades are much less expensive than the lighter ones. For these reasons, the process of the present invention which enables a greater utilization of natural dark pigmented material for the production of light stocks of good quality is of substantial economic advantage to the industry.

We claim:

1. A continuous process for bleaching pigmented keratinous fibers which comprises forming the fibrous material to be bleached into a web-like belt, passing the fibrous belt through a mordant solution consisting cssentially of a 1-20'% by weight aqueous ferrous salt solution maintained at a temperature of from about to 200 F. and at a pH of from about 1 to about 3 for a period of 10 to 150 minutes, passing the mordant solution treated fibrous belt through a bleaching solution consisting essentially of a 0.55.0% by weight aqueous alkaline hydrogen peroxide solution maintained at a temperature of from about 100 to about F. and at a pH in the range of about 7 to about 9 for a period of from about 10 to 90 minutes, and thereafter passing said fibrous belt through an iron removal solution consisting essentially of a 02-40% by weight aqueous iron removal reagent solution, said reagent being selected from the group consisting of sodium formaldehyde sulfoxylate and oxalic acid, maintained at a temperature of from about to about 170 F., and rinsing and drying the fibrous belt.

2. A process according to claim 1 wherein the ferrous salt is selected from the group consisting of ferrous sulfate heptahydrate, ferrous acetate and ferrous ammonium sulfate.

3. A continuous process for bleaching pigmented keratinous fibers which comprises forming the fibrous material to be bleached into a web-like belt, passing the fibrous belt through a mordant solution consisting essentially of a 1-20% by weight aqueous ferrous sulfate heptahydrate solution maintained at a temperature of from about 100 to 200 F. and at a pH of from about 1 to about 3 for a period of 10 to minutes, passing the mordant solution treated fibrous belt through a bleaching solution consisting essentially of a 0.55.0% by weight aqueous alkaline hydrogen peroxide solution maintained at a temperature of from about 100 to about 125 F.

and at a pH in the range of about 7 to about 9 for a period of from about 10 to 90 minutes, and thereafter passing the fibrous belt through an iron removal solution consisting essentially of 02-40% by weight of an aqueous sodium formaldhyde sulfoxylate solution maintained at a temperature of from about 125 to about 150 F. and at a pH in the range of from about 3.5 to about 4.5 for a period of from about 10 to about 40 minutes, and rinsing and drying the fibrous belt.

References Cited UNITED STATES PATENTS 2,868,615 1/1959 Bell 8-111 2,914,374 11/1959 Harris et al. 81 11 LEON D. ROSDOL, Primary Examiner. MAYER WEINBLATT, Examiner. 

1. A CONTINUOUS PROCESS FOR BLEACHING PIGMENTED KERATINOUS FIBERS WHICH COMPRISES FORMING THE FIBROUS MATERIAL TO BE BLEACHED INTO A WEB-LIKE BELT, PASSING THE FIBROUS BELT THROUGH A MORDANT SOLUTION CONSISTING ESSENTIALLY OF A 1-20% BY WEIGHT AQUEOUS FERROUS SALT SOLUTION MAINTAINED AT A TEMPERATURE OF FROM ABOUT 100 TO 200*F. AND AT A PH OF FROM ABOUT 1 TO ABOUT 3 FOR A PERIOD OF 10 TO 150 MINUTES, PASSING THE MORDANT SOLUTION TREATED FIBROUS BELT THROUGH A BLEACHING SOLUTION CONSISTING ESSENTIALLY OF A 0.5-5.0% BY WEIGHT AQUEOUS ALKALINE HYDROGEN PEROXIDE SOLUTION MAINTAINED AT A TEMPERATURE OF FROM ABOUT 100 TO ABOUT 125*F. AND AT A PH IN THE RANGE OF ABOUT 7 TO ABOUT 9 FOR A PERIOD OF FROM ABOUT 10 TO 90 MINUTES, AND THEREAFTER PASSING SAID FIBROUS BELT THROUGH AN IRON REMOVAL SOLUTION CONSISTING ESSENTIALLY OF A 0.2-4.0% BY WEIGHT AQUEOUS IRON REMOVAL REAGENT SOLUTION, SAID REAGENT BEING SELECTED FROM THE GROUP CONSISTING OF SODIUM FORMALDEHYDE SULFOXYLATE AND OXALIC ACID, MAINTAINED AT A TEMPERATURE OF FROM ABOUT 130 TO ABOUT 170*F., AND RINSING AND DRYING THE FIBROUS BELT. 